A system and method for making improved eyeglass temples by shot-injection molding a hard, thermoplastic material or other temple substrate materials with an enclosed reinforcing wire core are disclosed. The resulting eyeglass temples are firm and rigid, providing necessary stability while remaining pliable enough to be adjusted without the use of heat. The wire core is entirely encased by the temple material and helps the temple keep the shape that it has been adjusted to during patient fitting of the eyewear, even in hot temperatures, which can cause traditional temples to lose their shape. The shot-injection process includes partial filling of the mold with a first shot of the temple substrate material in a molten condition. The first shot is provided in an amount and viscosity that accommodates a first portion of the wire core and maintains the entire core in a desired position within the mold and material but without contacting the mold or other support. The wire core is then shot-injected into the material within the mold in a desired position that is maintained by contact of the first portion of the core with the material and without need for contact with the mold or external supports. The first shot amount of molten temple substrate material is also selected to permit displacement of the material during the shooting process but is also selected to avoid waste of the substrate by overflow during the shooting of the wire core. A second shot of temple substrate material is supplied in an amount sufficient to completely fill the mold to surround and encase the remaining portion of the wire core, bringing the material into close contact with the surface of the wire core. This second shot can also be selected to provide sufficient additional material to avoid undesirable shrinkage deformation of the finished temple during cooling. Additionally, the disclosed shot-injection molded reinforced temple can be at least partially coated with a second material in a second injection molding process, known as overmolding. The use of a second material, such as nylon, provides additional design options not available for temples that are not overmolded. The overmolding of a second, softer material onto the harder plastic improves a wearer's comfort by allowing for a more protective and comfortable fit and feel of the temple against the wearer's head. The wearer's comfort can be further improved by strategically placing the second material on the interior surface of the temple that rests against a wearer's head. Thus, the second material can either increase the aesthetic value of the temple and/or the gripping action of the temple. Further, the second material can be dyed or tinted different colors to improve the design of the temple by creating either a dual color or single color temple.
Plastic eyeglass temples having a wire core to reinforce and stabilize the temple are well known in the industry. As mentioned previously, the wire core allows the temple to be adjusted to more comfortably fit along a wearer's head and behind the ears. Generally, an Eye Care Professional (ECP) adjusts the temples of a pair of eyeglasses to fit the wearer. This is typically done by warming and molding the shape of the temple to create a better fit. Unlike temples without a wire core, plastic temples with a wire core will not lose their shape when the temple is warmed, such as by being left in a car on a warm day.
Plastic eyeglass temples have been produced in a variety of different manners. Milling has traditionally been used to produce temples made from acetate. The resulting milled temples can have a wire core manually pressed or ultrasonically embedded into the temple. This is usually accomplished by placing the milled temple flat, warming the temple, and pushing a wire core sideways along its longitudinal axis into the temple. The wire core can also be laminated into the temple by sandwiching the core between two preferred temple portions and then heating the portions until they form around the core and join together.
Another method for producing eyeglass temples is by injection molding, which is generally used to produce plastic or nylon temples, sunglass frames and sunglass frame parts. Such injection molding usually involves molding a temple in a single plastic material. One known method used to include a wire core in the temple requires placing the entire wire core in the temple mold prior to injection of the desired material into the mold. This is also referred to as insert molding. Positioning of the wire core during traditional injection molding is problematic in that the core has to be maintained in its desired position by some form of contact support means provided by the mold or externally, which makes it difficult if not impossible to completely surround the wire core with molten temple substrate material without creating some gaps in the temple material and/or other molding defects such as sink marks or bubbles.
Metal eyeglass temples are also known in the art. Although metal temples are durable, they present wearer comfort issues, particularly where the end portion of the metal comes into contact with the wearer's ears and/or along the wearer's temple and head. The art has attempted to address such comfort issues by cladding the ear end portion of metal temples with an end piece made from plastic or rubber. For example, Yashahara et al. U.S. Pat. No. 7,490,934 discloses an end piece for a metal eyeglass temple formed about the ear end portion of the metal temple. The end piece comprises a central flexible member such as an elastomeric rubber located between two hard end members formed in an integral manner at each end of the flexible member. The metal temple's ear portion is inserted into the end piece through an insertion hole extending inside and between the hard end members and the central flexible member. Insert molding is disclosed as one method of integrally forming the two hard end members into the flexible member portion of the ear piece. Use of such hard members is disclosed or necessary to present rotation of the flexible end piece around the axial core provided by the wire temple. This approach leaves a portion of the metal temple uncovered by the flexible or hard members.
Asano U.S. Pat. No. 6,598,969 discloses another method for making end pieces for metal eyeglass temples with the metal temple serving as the core of the end piece. The disclosed end pieces comprise two plastic materials, an end piece substrate material and a relatively softer end piece cover material. The end piece is formed by conventional injection-molding, press-molding or cast-molding. The end piece substrate and cover material are formed in advance and joined by adhesives or heat-welding, or the cover material is injected molded over the substrate. Alternatively, the end portion of the metal temple is used in insert-molding or shooting molding into the substrate layer and, after the substrate layer solidifies, the cover material is applied to the substrate. This leaves a portion of the metal template unclad by either substrate or cover material.
The use of entire metal temples partially clad with end pieces disclosed in the above-mentioned prior art is also disadvantageous in that the eyeglass frame weight is increased by that combination over metal-only temples.
More recently, Hardy U.S. Pat. No. 7,878,647 sought to overcome some of those problems by use of plastic eyeglass temples comprising a receiver portion and an ear piece portion formed from two different plastic materials. A cavity is provided within the receiver portion within which the proximal end of the pliant support member (wire core) is located. The flexible ear piece portion can be formed by molding around the cavity end of the receiver and the wire core. The disclosed methods involve providing a mating portion on the receiver that is surrounded by the flexible ear piece material during subsequent molding of the flexible ear piece portion onto the receiver portion.
Hardy's plastic temple and methods for making them thus includes complicated features and steps, including the need to correctly position the flexible wire core within two different materials during molding, the use of two temple materials, and use of special mating portions pre-formed on the receiver end of the temple. The ear piece portion of Hardy's temple is also constructed entirely of flexible material, causing a necessary but lesser desired compromise between the need to use softer materials for the ear piece portion to provide greater user comfort at the expense of sacrificing better fitting shape retention qualities provided by harder temple materials.
There is therefore a need in the art for reinforced plastic eyeglass temples that provide improved wearer comfort without sacrificing fitting and shaping of the temple to the individual wearer, and simplified methods for their manufacturer.